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Regensburg 2000 – scientific programme

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HL: Halbleiterphysik

HL 16: Störstellen/Grenz- und Oberfl
ächen I

HL 16.6: Talk

Tuesday, March 28, 2000, 10:45–11:00, H17

Photovoltage phenomena in sintered porous layers of TiO2 — •Volodimyr Duzhko1, Victor Timoshenko2, and Thomas Dittrich11Technical University Munich, Physik Department E16, D-85748 Garching, Germany — 2M. V. Lomonossov Moscow State University, Faculty of Physics, 119899 Moscow, Russia

Sintered porous layers of TiO2 nanocrystals (with different

mean diameter between 5 and 60 nm) were investigated by methods

of pulsed and spectral photovoltage in the spctral range from

1 to 4 eV. The sign of the photovoltage was found to be positive.

The photovoltage amplitude depends on the mean diameter of the

nanocrystals and on the traps induced by adsorbed molecules. The

photovoltage amplitude increases irreversibly by more than 2

orders of magnitude after short vauumation of freshly prepared

porous TiO2 layers. This effect correlates with an increase

of the rise and decay times of the photovoltage transients.

Further, the photovoltage amplitude increases with increasing

diameter of the TiO2 nanocrystals. The mechanism of the

formation of the photovoltage signal in in porous TiO2 is

discussed on the basis of excess carrier diffusion and trapping

leading to optical doping of TiO2 nanocrystals.

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